The quest for ever greater miniaturization of electronic interconnect devices imposes stringent and challenging processing standards in general, and in particular in the areas of wafer flatness or planarity. The challenge stems, inter alia, from the multitude of differing metals/materials used at the various levels. Specifically, copper which is greatly favored as interconnect metal because of its attractive electrical conductivity and low cost, presents special planarity challenges, due to its chemical reactivity that makes it prone to oxidation/erosion, believed by many to be the cause of dishing.
To achieve optimum planarization, the industry increasingly relies on mechanical chemical polishing (CMP) at each manufacturing level.
Broadly, there are two types of CMP processes:    A. Slurry-based CMP compositions, wherein abrasive particles along with other ingredients are dispersed in aqueous/solvent media, and are delivered onto a pad, typically made of polyurethane or polyurethane composites. The surface to be planarized is rubbing against the rotating pad resulting in a leveling action via removal of protruding/uneven matter.    B. Fixed abrasive pads, wherein abrasive particles are embedded in the polishing pad. Fixed polishing systems are gaining popularity because they lead to better planarity. Also, fixed abrasive systems generate less waste, as they do not require delivery of extraneous slurry.
Abrasive materials utilized both in slurry suspensions and fixed abrasive pads, are typically a blend of particulate metal oxide particles, generally selected from the group of oxides of silicon, cerium, aluminum, titanium, and others.
Slurry-based systems present difficulties, some of which are:    1. The slurry suspensions are prone to stratification/settling that tends to make the suspension non-homogeneous and unstable that can lead to uneven, non uniform slurry delivery, resulting in uneven planarity. This is caused at least in part, by the multiplicity of metal oxide particles in the slurry blend, with each metal oxide having individual and potentially dissimilar surface properties.    2. Slurry particles tend to “stick” to the polished wafer, leading to particulate surface contamination, that makes the wafer difficult to clean satisfactorily.    3. Spent or waste slurry particles can clog the grooves of the polishing pads, again resulting in uneven slurry delivery and unsatisfactory planarization.
Referring to fixed-abrasive pad systems, they tend to yield improved planarity, compared to slurry-based systems, but because of the hydrophobic nature of the abrasives embedded in the polymer matrix, are often prone to poor wettability.
The prior art recognizes the need for improved abrasive particles, to better serve the industry's challenging needs. This need is reflected in part by U.S. Pat. No. 6,582,623 to Grumbine and U.S. Pat. No. 6,592,776 to Wang, that are indicative of the more recent prior art. They disclose abrasives that are “surface-modified” via organic silanes, and/or via nitrogen-containing compounds, such as benzotriazole (referred to as “film-forming agents”), and at least one silane compound. The thus surface-modified abrasives are reported to afford tailoring a given polishing composition for a specific task, to achieve a desired polishing rate, to suit the nature of material to be polished, etc. The surface-modified abrasives are also said to reduce agglomeration and settling of the slurry dispersions. Surface modifiers are contained in a solvent which, when added to the dispersion leads to the bonding of the surface-modifying moiety to the abrasive particle.